Kurzban’s own progress through academe has involved some detours. Raised in Poughkeepsie, New York, he attended Cornell University as an undergraduate, switching his major from biology to psychology. He attributes his interest in evolutionary psychology to “a couple of really important moments,” including his discovery of Margo Wilson and Martin Daly’s classic 1988 book, Homicide, and a talk by David M. Buss, now professor of psychology at the University of Texas at Austin and author of The Evolution of Desire: Strategies of Human Mating (1994; revised in 2003).

“If you really want to trace the roots [of evolutionary psychology], you start with Darwin obviously,” says Kurzban, but the discipline’s more recent forebear is sociobiology, the controversial Darwinian study of animal and human behavior introduced by Harvard entomologist E.O. Wilson in his 1975 book, Sociobiology: The New Synthesis. The reliance on evolutionary models to explain human behavior made headlines at the time, and Wilson, an ant expert, was widely derided as a biological determinist, a defender of the status quo, and even a racist.

Since then, however, sociobiology has birthed two disciplinary offspring: Human behavioral ecology, which studies real-life fitness outcomes, and evolutionary psychology, which focuses on what Tooby and Cosmides called “the adapted mind.” Although the evolutionary paradigm still has its critics, who say it undervalues the role of culture, its influence is, without doubt, spreading and transforming both the social sciences and humanities.

Integral to evolutionary psychology is the notion of modularity. “In the same way that you’ve got a liver and a kidney which do special things,” Kurzban explains, “you have things in your brain which do special things. So we shift the debate from nature-nurture, which we think is not an interesting way to frame it, to, ‘What are the functional mechanisms in your head that do really specific jobs?’ We see ourselves as reverse engineers. We take a thing, look at what it does, and then try to figure out how it was built.”

Kurzban recalls his early excitement at the field’s potential. “Once you shine that conceptual light on questions in psychology, I see vistas of research opening upand clarity of thought that was very enticing [to me] as a young person,” he says. “And still is.”

But first, after graduating from Cornell in 1991, he decided to indulge another love. “I’ve always been a big fan of Disney,” he says. Though he’d been told no jobs were available, he loaded up his Nissan Sentra and drove to the company’s headquarters in Orlando, Florida. When he arrived at the “casting office,” he recalls, “their interview was one question: ‘Why do you want to work at Disney?’ I told them I loved it and wanted to be part of the family. And they asked me when I could start.” (If only landing academic jobs were as easy…)

For six months, Kurzban worked at Epcot Center, running attractions, and then, with his high-school French, snared a gig at Euro Disneyland a few miles east of Paris. He sent his graduate school applications off from France.

When Cosmides, now co-director of the Center for Evolutionary Psychology at the University of California at Santa Barbara, agreed to accept Kurzban as a student, “that was a pivotal moment in my trajectory,” he says. In truth, he had hoped for the chance to study with Buss, then at the University of Michigan, but was turned down. Over time, though, the emphasis at Santa Barbara on social psychology served him well. “The fit there turned out to be very good,” he says.

His next step was two years of post-doctoral work at the University of Arizona, at the behavioral economics laboratory of Vernon Smith, who would go on to win the Nobel Prize in economics. Kurzban says the methods he learned thereincluding using real money in experiments to gauge costs and benefits to his subjectsremain part of his laboratory practice today.

Then came two more years as a post-doc, split between the California Institute of Technology’s Division of Humanities and Social Sciences and the University of California at Los Angeles’ anthropology department. “Four years of post-doc is unusual,” Kurzban says candidly. “You start asking yourself, ‘Why can’t this guy get a job?’”

And, for a while, he couldn’t. “I applied every year of my post-doc,” he says. “It was a tough time, not that many people really want to hire someone trained like me, my publication stream was not as strong as it could have been, the market is ficklethat’s hard. But if we’re going to be honest, I was looking for a job, and I couldn’t get one, and I feel very lucky to have had the opportunity to come here to Penn.”

At Penn, Robert Seyfarth, professor of psychology and an expert on animal behavior, says that the department was eager to increase its strength in evolutionary psychology, “a really exciting area.” Kurzban, he says, is “part of a new wave of social psychologists” emphasizing evolutionary approaches, and his ability to integrate work in decision sciences and economics with evolutionary theory and social psychology made him particularly attractive. For his part, Kurzban, who came to Penn in the fall of 2002, says he appreciates the strong biological grounding of the University’s psychology department.

This spring, Kurzban taught a 9 a.m. undergraduate class on human sexuality, in which sufficiently caffeinated students caught flashes of his wry wit. “OK, number of sexual partners is something that people are very interested in,” he said as he quickly reviewed survey data. “People around the world have an average number of 10.5 sexual partners. Typically, people’s actual number of sexual partners is an integer.”